Last spring as my wife was preparing to take her college choir on a trip across Europe, we were discussing how to keep in touch with the whole group easily. It is always a little nerve wracking when students are spread out across an airport terminal or sight seeing in a foreign country and the need arises to reach everyone. Time can really be of the essence in those situations, especially if the itinerary needs to change on a moments notice.
It occurred to me that Twitter might be a viable option for a mass contact tool. If you don't know much about Twitter, I'll explain it briefly as a service that people use for posting information, thoughts, or status updates. So it is basically like the status box in Facebook for those of you familiar with that feature. Twitter does a few other things, but not much. It really is focused on these brief 140 character updates, which are fondly referred to as "tweets."
Well, one of those "other things" that Twitter does is allow a user to receive updates from someone as a text message on their mobile phone. It was this feature that appealed to me, because it seemed to me that my wife could post one "tweet" and, provided all the students were "following" her, they would all receive the tweet instantly as a mobile text. We decided to try it. Over the next few weeks the students registered for Twitter, requested to be able to "follow" my wife's updates (which were set to private), and checked the box for receiving tweets from her via sms. Twitter sends a quick verification text to your mobile phone and then you're all set for getting tweets as sms. The whole process from registration to verification takes just a few minutes once you know the steps.
After a few tests stateside we were set. She ended up using this tool quite a bit, both in the various airports and across France and Austria. Any changes in plans were easily and instantly communicated to everyone. Worked like a charm, and sure beat trying to use a phone tree. If your groups travels a lot, it might be something you want to consider. If you students are younger and having Twitter accounts isn't a viable option, you could at least use it to communicate with your chaperones. It could also be a nice way to keep parents back home up to date as well. For example, you (the teacher) could have an account for communicating with the students and/or chaperones, and one chaperone could have an account for trip highlights that parents could subscribe to. In any case, let me know if you have any questions, I'm happy to help if you want to give this a try.
UPDATE: I now recommend www.sendgm.com over using Twitter for mass sms.